T&T: Interfacing autopilot and chartplotter

[Lewis Boone]

An update to my auto pilot,  chart plotter problem.

The Navico auto pilot will only accept APA, BWC, BWR and XTE NEMA
sentences, and from that list the chart plotter will only output BWC
and BWR. It also appears that the chart plotter output's NMEA version
2.3 and my auto pilot don't understand 2.3. I found the following info

The last version 2 iteration of the NMEA standard was 2.3. It added a
mode indicator to several sentences which is used to indicate the kind
of fix the receiver currently has. This indication is part of the
signal integrity information needed by the FAA. The value can be
A=autonomous, D=differential, E=Estimated, N=not valid, S=Simulator.
Sometimes there can be a null value as well. Only the A and D values
will correspond to an Active and reliable Sentence. This mode
character has been added to the RMC, RMB, VTG, and GLL, sentences and
optionally some others including the BWC and XTE sentences.

I was looking at the info on Brookhouse Multiplexes

http://brookhouseonline.com/nmea_multiplexer.htm

If I understand the documentation correctly using their multiplexer
the output from the chart plotter could be modified to conform to
something the auto pilot will understand.

Has anybody experience with this and is it a viable option.

Thanks to all who advised me with this problem. It is very much appreciated.



On 8/31/06, Lewis Boone <lewisgboone@gmail.com> wrote:
> I am unable to get my navico auto pilot PH 8000 to respond to commands
> issued from a R70RC Raymarine chart plotter. The auto pilot
> understands the commands from a navigation program on a laptop e.g.
> $ECBWC,183107,4420.66,N,07600.81,W,130.81,T,144.65,M,0.971,N,002*32
> $ECBWR,183107,4420.66,N,07600.81,W,130.81,T,144.65,M,0.971,N,002*23
>
> A sample from the chart plotter using hyper terminal
>
> $ECBWC,211611,4421.01,N,07600.90,W,112.5,T,126.0,M,0.72,N,GOTO CURSOR,D*68
>  $ECBWR,211611,4421.01,N,07600.90,W,112.5,T,126.0,M,0.72,N,GOTO CURSOR,D*79
>
> >From what I can see the sentence structures are identical, Why does it
> understand NMEA data from a laptop and not similar data from the chart
> plotter? Could there be different line feed or carriage return
> characters, maybe different voltages? Could feeding the data through a
> multiplexer solve the problem. I have tried everything I can thing of
> with no success, Does anyone have any suggestions.
>
> Thanks
> Lewis Boone
> 265 Poulin Ave #1705
> Ottawa, Ontario
> K2B 7Y8
> LewisGBoone@gmail.com